This is one reason I love the community. In order to understand light and how to use it properly, it helps to look at examples from real life, and other's use of light. With digital photography our ability to take pictures has greatly increased, we can change light on a whim. Sharing this information has also increased.
I was made aware of a website that is a great asset to the sharing of this information in particular. Take a look at this website, there's a few things missing about the information it can share, but most of the uploaders and community have tried to assist where it's missing.
This website shows not only the end photo, but a setup of the lighting, and some other photograph exif information. This can help you understand the lighting setup, but it will also help you understand how to light your own scenes. Taking a look at the photos available you can get an understanding of how to correctly light your key objects in your scene, while still providing light to the background, or removing light completely from your background, yet still having enough light to provide a well lit render.
So again it's shortcomings, you don't get a little information about the lighting position and strength, but you can assume some things for example the height. Understand distance and direction, assume height and strength. Set up your own scenes to reflect what you learn from this website.
Additional things that are missing is the type of light. Understanding distance and strength affects the hardness and fall-off, but the type of light, including the size, shape and color, also affects it too.
I'm still working on setting up some examples of lighting a scene for the next tutorial... probably finish it up this weekend.